Plasma dicing, also referred to as deep reactive ion etching, is a dry etching technology used to singulate dies from semiconductor wafers. Plasma dicing can be implemented as a parallel process to dice whole semiconductor wafers simultaneously and therefore more quickly than a laser, for example, which gradually singulates dies using multiple passes.
When compared with a saw singulation process, plasma dicing also minimizes cutting kerf, leaving more of a semiconductor wafer intact, and reduces mechanical damage imparted to the edges of dies resulting from the singulation of the wafer. Sawing with a diamond-tipped blade can leave a saw street roughly 85 microns wide as compared to approximately 5 to 10 microns in width for plasma dicing. Stresses and microcracks caused by the mechanical interaction between the saw blade and a semiconductor wafer can lead to failures in the resulting dies when they are operationally cycled in power and temperature. Edge damage from sawing is increasingly likely with thin dies having a thickness of 50 microns or less. Even absent sawing, damage to a die edge can occur after singulation from routine handling.
Particular dies benefit from being manufactured with a metal backing. A metal back layer adds strength to thin dies and also provides advantageous thermal, electronic, and electromagnetic (EM) properties. A metal backing can operate as a heat sink for a power chip, as a common ground for a chip's multiple electronic components, or excite certain EM wave propagation modes for a radio frequency (RF) chip.
The standard method of providing a metal backing on dies is to deposit a metal layer on the back side of a semiconductor wafer before singulating dies from the wafer.
Singulation is typically carried out via sawing. While plasma dicing is preferable for singulating semiconductor wafers, the dry etching technology is incompatible with metal.
The present disclosure is illustrated in part with examples, as reflected by disclosed embodiments, and is not limited by the accompanying figures, in which like reference numbers indicate similar elements. Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to the dimensions of other elements to help to improve understanding of embodiments implicitly or explicitly disclosed herein.
The apparatus and method components have been represented, where appropriate, by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present disclosure so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. Also, the operations included in the flow diagrams do not imply a required order in performing the functionality contained therein.